Internal combustion engines, including diesel engines, gasoline engines, gaseous-fueled engines, and other engines known in the art, may exhaust a complex mixture of air pollutants. These air pollutants may be composed of gaseous compounds and solid particulate matter. Solid particulate matter may be recognized as soot entrained within black smoke emitted from the engine. Due to increased attention on the environment, exhaust emission standards have become more stringent and the amount of black smoke emitted from an engine may be regulated depending on the type of engine, size of engine, and/or class of engine.
It has been established that the amount of fuel available for combustion relative to the amount of air simultaneously available (fuel to air equivalence ratio), is directly related to the amount of black smoke produced and emitted from an engine following combustion of the fuel/air mixture. For example, a higher fuel to air equivalence ratio will result in a greater production of smoke, while a lower fuel to air equivalence ratio will result in a lower production of smoke. For this reason, a vehicle that meets black smoke regulations at sea level may fail to meet the same regulations at altitude, because of the decreasing atmospheric air density at altitude.
One method that has been implemented by engine manufacturers to meet black smoke regulations at altitude has been to limit fuel delivery to the engine according to altitude. One such method is described in U.S. Pat. No. 4,368,705 (the '705 patent) issued to Stevenson et al. on Jan. 18, 1983. The '705 patent describes an electronic engine control system having a plurality of engine maps. During operation of an engine, the electronic engine control system references a first map to determine a maximum fuel/air ratio for sufficient combustion to meet emission standards as a function of current engine speed. The maximum fuel/air ratio is then supplied to a multiplier along with a current intake manifold air pressure to determine a maximum amount of allowable fuel to be injected per engine stroke. The electronic engine control system then references current ambient air pressure with a second map to retrieve an altitude derating multiplier, and applies the derating multiplier to decrease the maximum amount of allowable fuel. This decreased maximum amount of allowable fuel is then used to limit the amount of fuel introduced to the engine during a single stroke of the engine such that black smoke production at varying altitudes may be reduced.
Although the electronic engine control system of the '705 patent may reduce black smoke production at altitude, it may be limited and inefficient. In particular, because the altitude derating multiplier is only based on ambient air pressure and does not vary according to any other engine parameters, it may inaccurately control the production of smoke throughout the operational range of the engine. For the same reason, the electronic control system of the '705 patent may unnecessarily limit some portions of the engine's operational range, resulting in inefficient operation.
The control system of the present disclosure solves one or more of the problems set forth above.